The present invention relates generally to mobile apparatuses for pulling cables through an underground conduit and, more particularly, to an articulated cable puller that positions an element, such as a sheave or the like, that is secured on the end of a boom of the apparatus at a precise location with respect to the vehicle on which the apparatus is mounted.
Public utilities use large amounts of underground electrical cable, such as electric power cable, telephone and telegraph cable. In addition, there are underground railroad and other public transportation cable systems, fire and police department cable systems and traffic control signal generation cables and the like. The preferred place of installation for these types of cables is below ground in conduits which protect the cables from weather. In addition, underground cables do not disrupt the environment, either from an aesthetic point of view or from the very real practical problem of supporting many cables on overhead lines. Overhead lines have the further disadvantage of being susceptible to vandalism. In addition, they present potential danger to the population when cables may fall because of accidents, storms and the like.
However, even the best underground cable systems ultimately deteriorate. Underground cables that deteriorate must be replaced. Furthermore, the extensive increase in the use of fiber optic cables has made it desirable to replace cable presently existing with larger, faster, better or otherwise different cables.
The process of cable installation can be expensive and difficult, particularly when many cables are packed together and separated by 400 to 800 feet intervals, which is the typical distance between manhole locations in cities.
Industry has been installing larger and more complex cables which require greater pulling forces to install. Furthermore, in congested areas such as large cities, cables are being positioned at a depth which is 10, 20 or even up to 30 feet below the surface of the pavement. As cables have grown larger and become located deeper, it has become more and more desirable to pull cables in a horizontal direction aligned with the longitudinal axis of the conduit. Pulling a cable in line with the conduit makes the most efficient, and thus effective, use of a given pulling force.
In response, the apparatus illustrated in U.S. Pat. Nos. 5,193,785; 5,209,457 and 5,232,205 to McVaugh was developed. In these patents, an extensible mechanism, such as a boom, is disclosed which features a sheave on one end and a pulling wheel near the other end. The boom may be positioned in a generally vertical orientation so that the sheave is placed in alignment with the longitudinal axis of the conduit. The cable, as it is pulled through the conduit, travels horizontally to the sheave. This allows the force pulling the cable out of the conduit to be aligned with the longitudinal axis of the conduit.
The positioning of the boom by the apparatus disclosed in the McVaugh '785, '457 and '205 patents, however, is limited. It is only possible to lower the boom of the apparatus from the back of the truck upon which it is mounted. The location of a manhole, for example, may require that the boom be lowered from the side of the truck. Furthermore, the arrangement of the hydraulic cylinders supporting the boom disclosed in the McVaugh '785, '457 and '205 patents limits the range of motion of the boom, and thus the positioning of the sheave positioned upon its end. Additional flexibility in positioning the sheave is necessary, for example, when the longitudinal axis of the conduit to be accessed does not intersect the manhole when viewed from above/in plan.
Accordingly, it is an object of the present invention to provide an articulated cable puller that permits cable to be pulled through conduits in a horizontal direction, thereby optimizing the efficiency of the cable installation apparatus.
It is another object of the present invention is to provide an articulated cable puller that allows cable to be pulled from the back or side of the vehicle supporting the apparatus.
It is another object of the present invention is to provide an articulated cable puller that features increased flexibility in terms of positioning a boom, and thus a sheath or other cable guiding device positioned on its end, within a manhole or similar location.
It is still another object of the present invention to provide an articulated cable puller that features a strong support structure for the boom.
Other objects and advantages will be apparent from the remaining portion of this specification.